Related National Programs

1a.Objectives (from AD-416):
Objective 1: Conduct a controlled, vitamin D supplementation trial in volunteers with vitamin D insufficiency (VDI) to determine if supplementation to achieve the proposed level of >75 nmol/L for maintenance of bone health is also appropriate for maintenance of immune function. Sub-objective 1A. Determine if supplements decrease the production of proinflammatory and increase the production of anti-inflammatory cytokines and chemokines by innate immune cells stimulated ex vivo. Objective 1B. Determine if supplements decrease serum markers of inflammation and autoimmune activity, and increase serum levels of defensive molecules. Objective 1C. Determine if supplements decrease blood levels of proinflammatory T-helper type 1 (Th1) and Th17 cells and increase levels of anti-inflammatory T-regulatory (Treg) and Th2 cells.
Objective 2: Determine the impact of plant polyphenols and polyphenol-rich foods on immune cell function using cell culture systems, mouse models, and human volunteers. Examine anti-inflammatory and anti-cancer activities of polyphenols in animal models, as well as inflammation and oxidative damage in studies with human volunteers, including overweight/obese individuals. Objective 2A. Analyze the effects of polyphenol-rich foods and individual plant polyphenols on immune cell function in vivo and ex vivo. Ojective 2B. Examine anti-inflammatory activities of polyphenol-rich foods, individual plant polyphenols and vitamin A in mice and humans who are at risk for developing inflammatory disease, such as autoimmune mice and obese humans. Objective 2C. Evaluate the anti-cancer activity of polyphenol-rich foods and individual plant polyphenols.
Objective 3: Examine the absorption of B-cryptoxanthin (CX) from supplements and foods, its contribution to vitamin A stores, and the impact of CX, other carotenoids and vitamin A on immune function. Objective 3A. Measure the absorption and metabolism of CX from Satsuma mandarin juice fed to healthy adult humans. Objective 3B. Estimate the impact of daily consumption of food sources of CX or B-carotene (BC) on plasma and breast milk concentrations of CX, BC and retinol in lactating women. Objective 3C. Determine the impact of CX on immune and bone marker status in the Mongolian gerbil.
Objective 4: Determine if high-level vitamin A intake is associated with higher Th2 and Treg responses and lower Th1 and Th17 responses relative to adequate and deficient intake. Objective 4A. Using dietary and targeted gene disruption approaches in mice, determine if vitamin A enhances Th2 and Treg responses by acting directly on T cells. Objective 4B. Using subjects recruited in the vitamin D supplementation trial described under Objective 1, determine if vitamin A status is associated with higher blood levels of NK, NK-T, Th2 and Treg cells, and lower levels of Th1 and Th17 cells.
Objective 5: Identify the role of dietary selenium and selenoproteins in regulating cellular responses to oxidative stress. Objective 5A. Identify the pro-inflammatory and anti-inflammatory proteins S-glutathionylated by selenoprotein W. Objective 5B. Determine the role of selenoprotein W in key inflammatory pathways.

1b.Approach (from AD-416):
The impact of selenium, vitamins A and D, and plant polyphenols, on immune function will be examined using cell culture systems, mouse models, and human intervention trials. The anti-cancer activities of polyphenols will be examined in animal models. Absorption of beta-cryptoxanthin will be examined in gerbils and humans. The effect of selenium on cell division and cell signaling will be examined in cell culture.
Replacing 5306-51530-013-00D (1/09).

3.Progress Report:
Objective 1: Recruitment of human volunteers for the study examining the effect of vitamin D supplementation on immune function was completed this year. Data analysis for the study is currently in progress. In addition, work with collaborating scientists continues to examine the effects of vitamin D supplementation on inflammation during pregnancy and during HIV infection. Objective 2A) Isolated lymphocytes were treated with physiological levels of resveratol glucuronide, the major metabolite of the plant antioxidant resveratrol, to define how this metabolite alters gene expression and function of these immune cells.
Objective 2B) The U.S. High Bush Blueberry Council awarded a collaborative grant to study whether feeding humans blueberries will decrease the inflammatory response to a fatty meal. This study is complete and data analysis is in progress. Objective 2C) Mouse studies completed in 2010 by us showed that feeding purified polyphenols at levels higher than typically found in foods did not kill leukemia cells. The diet studies planned for this year with polyphenol-rich foods will not be pursued as this approach is likely to be ineffective.
Objective 3:
(1) We used in vitro methods for analyzing stomach digestion of carotenoids and retinoids from foods to determine the effects of added oil on carotenoid absorption from mandarin oranges.
(2) We compared the effects of two food-based interventions, mandarin oranges and orange sweet potatoes, to positive and negative controls fed to Bangladeshi women with marginal vitamin A status. Beta-carotene concentrations increased in blood and breast milk of the group fed orange-fleshed sweet potatoes. Beta-cryptoxanthin concentrations increased in blood and breast milk of the group fed mandarin oranges. Vitamin A concentrations increased only in the blood and breast milk for the group fed vitamin A. Beta-cryptoxanthin was 4-fold more bioavailable than the beta-carotene and appeared in breast milk as well as serum. This study suggests that tangerines and perhaps similar fruits may be suitable for development as a food source for improving the vitamin A status.
(3) We completed the chromatography analysis for tissue samples from our gerbil study. Major accumulation tissues were the liver and adipose. Carotenoid accumulation in most tissues increased with increasing dietary intake.
Objective 4: The decision was made in a previous year that these studies would not be pursued due to insufficient funds.

Objective 5: We discovered that selenoprotein W:
(a) is required for the dimerization of the epidermal growth factor receptor;
(b) mediates hydrogen peroxide-stimulated activation of the epidermal growth factor receptor and the hepatocyte growth factor receptor;
(c) co-localizes with the epidermal growth factor receptor at the plasma membrane in starved cells; and,
(d) is rapidly degraded after cells are stimulated with epidermal growth factor.

4.Accomplishments
1.
Improving vitamin D status in at-risk populations. Vitamin D deficiency is common in US youth with HIV infection and optimal vitamin D dosing for treatment is unclear, particularly because some antiretroviral drug regimens affect vitamin D metabolism. ARS scientists from the Davis, California, worked with colleagues from the Adolescent Trials Network to conduct a one year, placebo-controlled intervention trial of monthly dosing with 50,000 units of vitamin D3 among 203 HIV-infected youth ages 18-24. The use of the antiretroviral efavirenz was associated with lower baseline vitamin D status, but this supplementation regimen was safe and improved vitamin D status regardless of antiretroviral regimen. This study demonstrated that at-risk youth benefit from vitamin D supplementation levels comparable to those recommended for the general population.

2.
Human lymphocyte function is affected by resveratrol glucuronide, a major in vivo metabolite of resveratrol. It is suspected that plant-derived antioxidants such as resveratrol, which is found in grapes and some berries, alter the activity of individual immune cells in the human body after consumption but specific mechanisms are not known. ARS scientists working at the Davis, California, location found that the major metabolite of resveratrol found in humans after ingestion, resveratrol glucuronide, altered gene expression in isolated T-helper lymphocytes, a type of white blood cell important in many immune responses. Such changes in gene expression suggest that changes in function also occurred. Further studies are in progress to define the mechanisms of action of this and other phytochemical metabolites generated in the body after consumption of a meal containing the parent compound. These results are novel and will help determine how plant antioxidants affect human health by modulating the activity of immune cells.

3.
Bioavailability of provitamin A carotenoids from mandarin oranges and sweet potatoes. ARS scientists in Davis, California, working with colleagues in Bangladesh, compared the effects of two food-based interventions, mandarin oranges containing beta-cryptoxanthin and orange sweet potatoes containing beta-carotene, on carotenoid bioavailability and vitamin A status in Bangladeshi women with marginal vitamin A status. Beta-carotene concentrations increased in blood and breast milk of the group fed orange-fleshed sweet potatoes, while beta-cryptoxanthin concentrations increased in blood and breast milk of the group fed mandarin oranges. Vitamin A concentrations increased only in the blood and breast milk of the control group fed vitamin A capsules. Beta-cryptoxanthin was 4-fold more bioavailable than the beta-carotene and appeared in breast milk as well as serum. This study suggests that mandarin oranges may be suitable for development as a food source for improving vitamin A status.

4.
Evaluation of biofortified cassava as a provitamin A-rich staple crop. Biofortified cassava, which was developed to combat vitamin A deficiency in Africa, also contains moderate amounts of beta-carotene. We estimated the effectiveness of biofortified cassava for increasing beta-carotene and vitamin A concentrations in ten healthy adult women. Data from this human study were combined with cassava consumption data from countries in Africa where cassava is a staple food, to model the daily vitamin A intake (and cyanide exposure, also contained in cassava) of women in Africa. If biofortified cassava completely replaced traditional low-carotenoid, white cassava in the diet, it could meet recommended vitamin A intakes for the following percentages of individuals from 6 African countries: Angola (95%), Central African Republic (95%), Congo (100%), Ghana (99%), Mozambique (99%), and Nigeria (92%). However, biofortified cassava loses substantial amounts of carotenoids during roasting when it is converted to gari, a traditional West African food made with cassava. Even so, this work demonstrates that consumption of biofortified cassava, processed to maintain beta-carotene and remove cyanide, can potentially increase vitamin A status in African populations and other areas of the world where cassava is a staple crop.

5.
Selenoprotein W regulates hydrogen peroxide activation of receptor tyrosine kinases. Dietary selenium supplements are popular and are thought to protect against cancer, but the scientific evidence is contradictory. Other studies suggest selenium increases the incidence of type 2 diabetes (a major risk factor for hypertension, stroke and cardiovascular disease). Dysfunctions in receptor tyrosine kinases cause many cancers and receptor tyrosine kinases control the insulin and cytokine signaling that may be altered in type 2 diabetes. ARS scientists in Davis, California, found that the selenium-containing protein, selenoprotein W, regulates hydrogen peroxide-mediated activation of receptor tyrosine kinases. Thus, selenoprotein W’s regulation of receptor tyrosine kinase activation by hydrogen peroxide may provide insight into a possible common mechanism in the development of chronic disease, including cancer and type 2 diabetes.